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Thursday, June 18, 2015

Helix design

When I decided that I would need a helix to do what I wanted to do on this layout I studied everything I could on the Internet and examined first hand any helix that I could. The room that I built in the back of my garage is a 20 x 10 ft rectangle but has a 2 ft bump out in one corner for part of the helix. The net space set aside for the helix is 42 x 42 inches.

I really liked the idea of using all thread rods to support the helix because it would allow me to experiment with some different grade adjustments plus it offered the best access to the tracks.

My design uses 90 degree curved sections of 1/2 inch plywood that are 4.5 inches wides. The radius on the outer edge of the curved sections is 20.5 inches. Between each section a pair of splicing blocks hold the sections together and attach to 3/8 inch all thread rod. Two 8-32 screws on each side of each section will secure the splice blocks to the curved sections.

I found that I could get 10 of the curved sections from a 4 x 4 sheet of birch plywood. After making the first one I marked it as master and used it as a template to draw the others.

The splicing blocks are made from scraps of the sheet that the curved sections were cut from in between 1/4 inch thick birch plywood material. The overall size of these assemblies is 4 inches x 2 inches.

Here are the results from a single 4 x 4 sheet of plywood. The curved sections on the left have been painted. All sections will be painted prior to assembly. This is a start, my plan is by doing some of this now, I'll be able to go right into assembling the helix after the yard is completed and installed.